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https://issues.apache.org/jira/browse/FLINK-3848?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15279989#comment-15279989
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Fabian Hueske commented on FLINK-3848:
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It turned out that the issue is more involved than I expected.
Here is my current working branch:
https://github.com/fhueske/flink/tree/tableProjectSource
[~dawidwys], I'll add some details about the challenges with this issue later.
Need some time to look into it again.
> Add ProjectableTableSource interface and translation rule
> ---------------------------------------------------------
>
> Key: FLINK-3848
> URL: https://issues.apache.org/jira/browse/FLINK-3848
> Project: Flink
> Issue Type: New Feature
> Components: Table API
> Reporter: Fabian Hueske
> Assignee: Fabian Hueske
>
> Add a {{ProjectableTableSource}} interface for {{TableSource}} implementation
> that support projection push-down.
> The interface could look as follows
> {code}
> def trait ProjectableTableSource {
> def setProjection(fields: Array[String]): Unit
> }
> {code}
> In addition we need Calcite rules to push a projection into a TableScan that
> refers to a {{ProjectableTableSource}}. We might need to tweak the cost model
> as well to push the optimizer in the right direction.
> Moreover, the {{CsvTableSource}} could be extended to implement
> {{ProjectableTableSource}}.
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